Abstract Number: 49

An underdiagnosed entity: papulonecrotic tuberculid

N. Allen 1, C. Zhao1,2, S. Chou2,3, P. P. Ferguson2,4, A. Kurien1

Meeting: 2021 Dermcoll

Session Information

Date: -

Session Title: Poster Presentations

Session Time: -

Introduction: Papulonecrotic tuberculid is a rarely reported cutaneous manifestation of tuberculosis (TB). It is thought to occur due to immune reactions to M. tuberculo- sis or its antigens within the skin, in individuals with strong anti-tuberculous cell-mediated immunity.

Case report: A 58-year-old otherwise well woman of Fili- pino descent was referred to dermatology with a 4-month history of tender ulcerated papules and nodules. Some lesions had central necrosis and pitted scarring. Her Man- toux test and Quantiferon gold were strongly positive. Vas- culitis screening was unremarkable. Skin biopsies were collected for histopathology and microbiology (including mycobacterium culture, bacterial culture, fungal culture and mycobacterium PCR). The histopathology demon- strated ischaemic necrosis and a caseating granuloma sug- gestive of papulonecrotic tuberculid. A pan-CT scan showed granulomata of the spleen and pancreas, but no abnormality in the lungs was identified. The microbiology investigations were negative. With the clinical presentation and classical histopathology, a diagnosis of papulonecrotic tuberculid was made. The patient has been referred to infectious diseases for antituberculous treatment.

Discussion: Only a portion of papulonecrotic tuberculid cases exhibit a confirmatory mycobacterial PCR. However, its classical clinical presentation with necrosis and scar- ring, histological findings of caseating granuloma, as well as its response to anti-tuberculous treatments reinforces its mycobacterial aetiology. This case represents a classical presentation of papulonecrotic tuberculid and raises aware- ness regarding the diagnostic pathway for the disease.